Programming Lab 5E Disk Drive Geometry

Programming Lab 5E
Disk Drive Geometry
Topics: Integer arithmetic.
Prerequisite Reading: Chapters 1-5
Revised: January 22, 2021
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Lab5E-Main.c
Background: A disk drive stores and retrieves data on one or more rotating
platters coated with magnetic material. There are two read/write heads per platter (one per surface), attached to an arm controlled by an actuator. The actuator
is used to position all the heads at a specific radial distance from the spindle,
thus selecting one of several concentric tracks on the surface of each platter.
Together, the selected tracks combine vertically to form what is referred to as
a cylinder; specifying a cylinder number thus determines the radial position of
the arm. The tracks are further divided into sectors of 512 bytes each, representing the smallest amount of data that can be read or written.
Locating a particular sector on the disk requires specifying a cylinder, a head
(or surface), and a sector. Cylinders and heads are numbered starting from zero,
while sectors are numbered starting from one. Modern disk drives combine the
physical cylinder, head and sector numbers into a single number called the
Logical Block Address (LBA) given by:
𝑙𝑜𝑔𝑖𝑐𝑎𝑙 𝑏𝑙𝑜𝑐𝑘 𝑎𝑑𝑑𝑟𝑒𝑠𝑠 (𝑙𝑏𝑎) =
(𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 × #𝐻𝐸𝐴𝐷𝑆 + ℎ𝑒𝑎𝑑) × #𝑆𝐸𝐶𝑇𝑂𝑅𝑆 + 𝑠𝑒𝑐𝑡𝑜𝑟 −1
Assignment: The main program will compile and run without writing any
assembly. However, your task is to create an equivalent replacement in
assembly language for the following function found in the C main program that converts a logical block address into the separate components
of cylinder, head and sector stored as components of a structure. The original C version has been defined as “weak” so that the linker
will automatically replace it in the executable image by the one you create in assembly;
you do not need to remove the C version.
typedef struct {uint16_t cylinder; uint8_t head; uint8_t sector;} CHS ;
void Log2Phys(uint32_t lba, uint32_t heads, uint32_t sectors, CHS *phy);
The equations for the physical cylinder, head and sector are given by:
𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 = 𝑙𝑏𝑎 ÷ (ℎ𝑒𝑎𝑑𝑠 × 𝑠𝑒𝑐𝑡𝑜𝑟𝑠)
ℎ𝑒𝑎𝑑 = (𝑙𝑏𝑎 ÷ 𝑠𝑒𝑐𝑡𝑜𝑟𝑠) % ℎ𝑒𝑎𝑑𝑠
𝑠𝑒𝑐𝑡𝑜𝑟 = (𝑙𝑏𝑎 % 𝑠𝑒𝑐𝑡𝑜𝑟𝑠)+ 1
The main program allows you to specify the total capacity of the disk by entering values
for the total number of cylinders, heads, and sectors. The slider is then used to select a
particular logical block address, which the program converts into the corresponding physical coordinates of cylinder, head and sector, and displays them on the screen.
x,y=(0,48)